Process for the production of silverless picture and sound records by the chromate method



Patented Feb 20, 1940 UNITED STATES PATENT OFFICE Q 2,191,011 f rnoCnss Foe "THE PRODUCTION OF s11,-

vEnLEss PICTURE AND soUNn RECORDS BY res nnoMA'rE METHOD 1 1 ltlax Bethe Hollaender,'Berlin-Friedenau, Geranany, assignor to Sifico A. G., Schafi'hausen,

I Switzerland No Drawing. Application November 22, 1937, Serial No. 175,982, In Germany December 1,

The suitability of the chromate method for the production of duplicate negatives and diapositives has been known for some time. As

1 special advantageof process, absence of grain and the straight line quality of the gradation have been praised. Thus David Writes (photographical Praktikuin, 6th edition, paged'rl l):

There thus arisesthat is,,according to the pinatype process-a picture shaded inthe high lights, half tones and shadowsinthe same sense a as on the original plate used for copying.

Now it was found, in contrast to such views, that this straight line quality of the gradation is only present when a considerable darkening of the high lights of the subject is accepted as 15 well, whereby, of course, thebrightnessof the projected image suffers. The sound strength is also affected to a considerably greater extent, since it is dependent on the density of the sound track and, in the variabledensity process, also on the density of the inoperative part of the sound track(seeEggert-Schmidt Einfiihrung in die Tonphotographie, 1932, page 69). In order to be able to make good copies, it is therefore necessary to work, in contrast to the opinions previously held in the lpinatype process, in

1 the region of the toe of the density curve of the chromate containing material.

This, however, cannot be if as has previously happened, a normal copy ready for pro- 30 jection is taken as the subject; for the light recordsand especially thesound records of normal copies are likewise situated more or less in the region of the toe of the density curve of carried out according to the present invention,

show a matt and chalky effect. The soundrec- 35 the material. employed. ,In a copying process a, 1 Claim. (01. 95-5) ord which, in the control mark process, extends still further than the image into the toe, would not only become considerably softer but also dis,-

torted, since as a result of the flatteningof the density curve, the assumption of undistorted reproduction-that is, the straight line quality of the transparency curvewould no longer exist.

These difficulties can be avoided by making density, curve of the silver, and, in fact, for

this purposeit will be necessary to go so far into the straight line curve as is necessary to obtain astraight line copy transparencycurve ofthe copy tobe projected, while making use of the toe of the chromated material. Thus,

ing to the inoperative position of the sound track, the subject may be given a blackening of,

, I claim:

Process for the production of silverless pictures and sound copies according to'the chromate method, consisting in producing an intermediate positive copy from a silver negative containing a picture and sound record on a silver salt sensitized positive film, the silver positive receiving such a density that the light parts of the picture as well as the sound record lie completely in the straight line of the gradation curve of the positive mat erial and producing a final copy from the said intermediate positive copy on a silt erless chroma-ts filmythe picture and sound record in said final chromate copy lying in the toe of the gradationcuriye,

MAX porno HCLLAE JER. 1

for instance, on the control marking correspond- 

